Walt Whitman (1819–1892) was an influential American poet, essayist, and journalist whose work boldly revolutionized the form and content of 19th-century American poetry. His magnum opus, 'Leaves of Grass,' originally published in 1855, was revised and expanded throughout his lifetime, and it stands as a landmark in the transition from transcendentalism to realism, embracing both views in a unique synthesis. Whitman's poetry is characterized by its free verse style and candid explorations of sexuality, nature, and the human spirit. He was often referred to as the father of free verse, breaking away from the strictures of traditional meter and rhyme to create a new, uniquely American poetic voice. In addition to 'Leaves of Grass,' his other works are compiled in collections such as 'WALT WHITMAN Ultimate Collection: 500+ Works in Poetry & Prose,' which showcases his extensive body of work beyond his most famous publication. As a poet and humanist, Whitman's work expressed his optimistic belief in democracy, the individual, and the interconnectedness of all living things, reflecting the diversity and vitality of the burgeoning American nation. His influence remains significant in the realm of American literature, resonating with later generations of poets and thinkers who pursued authenticity and a profound appreciation for the self within the collective experience of humanity.